The present invention relates to the field of medicine, and particularly to a novel 5-hydroxyl-1,7-naphthyridine compound substituted by aryloxy or heteroaryloxy, a preparation method thereof and a pharmaceutical use thereof.
Hypoxia inducible factor (HIF) is a section of transcriptional activator containing basic helix-loop-helix (bHLH) and PAS (Per/Arnt/Sim) that responds to the hypoxia conditions by mediating a series of gene regulation in biological cells. (Chowdhury, R., Hardy, A, Schofield, C. J., The human oxygen sensing machinery and its manipulation, Chem. Soc. Rev., 2008, 37, 1308-1319; Kaelin, W. G., Jr., Ratcliffe, P. J., Oxygen sensing by metazoans: the central role of the HIF hydroxylase pathway, Mol. Cell, 2008, 30, 393-402; Schofield, C. J., Ratcliffe, P. J., Oxygen sensing by HIF hydroxylases, Nat. Rev. Mol. Cell. Biol., 2004, 5, 343-354).
In 1992, during the study of erythropoietin (EPO, an erythropoiesis-stimulating hormone), Wang et al. found the transcriptional activator that stimulates the generation of EPO in hypoxic cells, and thus named it Hypoxia Inducible Factor, abbreviated as HIF. HIF is essential for cellular adaptation and survival to hypoxia, and the experiments show that under the effect of HIF, cells can still survive even if the oxygen content in the cells is reduced to 1% from normal 20%.
HIF consists of two subunits, HIF-a and HIF-b. HIF-a contains an oxygen-dependent degradation domain (abbreviated as ODDD), which is a key element unit in response to cellular oxygen content. HIF-a can form a stable dimer with HIF-b. After this dimer enters the nucleus, it activates the expression of important enzymes or enzyme systems such as glucose metabolism-related enzymes, GLUT-1, erythropoietin and vascular endothelial growth factor (VEGF), and thus resists the cell hypoxia conditions. HIF-b is a type of aryl hydrocarbon nuclear translator (abbreviated as ARNT), which forms a heterodimer with HIF-a to activate transcription of downstream genes.
To date, three HIF-a subtypes have been discovered, HIF-1a, HIF-2a, and HIF-3a, respectively. HIF-1a, first discovered by Wang in 1995, is widely expressed in human and mouse bodies. HIF-2a was isolated and identified in 1997, which has a protein sequence with 48% similarity to that of HIF-1a and therefore has the similar functions to HIF-1a, however, HIF-2a is only expressed in lung, endothelium and carotid artery. HIF-3a is a newly discovered HIF-a subtype, and little research has been done on it yet.
Studies have shown that the expression of HIF-a in cells is not affected by oxygen content, but HIF-a cannot stably exist in the cells having normal oxygen content, and has a half-life of only 5 minutes. HIF-a can only be stable under hypoxic conditions and thus play the normal function of activation of downstream transcription factors. In the cells having normal oxygen content, the prolyl at positions 402, 564 in the ODDD region of HIF-a was oxidized by prolyl hydroxylase to form 4-hydroxyprolyl, so that HIF-a cannot be dimmed with HIF-b, but soon binds to pVHL protein and then be degraded, and therefore cannot play an anti-hypoxia function. Prolyl hydroxylase (also abbreviated as PHD or EGLN), which plays a key role in the degradation of HIF-a, is a 2-oxoglutatone (2-OG)-dependent oxygenase. With 2-OG and divalent iron ions as prosthetic groups, PHD transfers an oxygen atom to the 4-position of the prolyl molecule to form a hydroxyprolyl, and meanwhile converts 2-OG into one carbon dioxide molecule and succinic acid. Both 2-OG analogs and divalent nickel, cobalt and manganese ions can antagonize the oxidation of prolyl in HIF-a by PHD, and inhibit the degradation of HIF-a, so that HIF-a can successfully be dimmed with HIF-b, and thus stimulates the downstream transcription factors, and ultimately plays an anti-hypoxia function. Studies have found that PHD has three subtypes: PHD1, PHD2, and PHD3. Further studies suggest that inhibition on PHD1 can help to treat skeletal muscle cell degradation, can protect myofibroblasts under ischemic conditions, treat inflammatory enteritis and colitis, and treat heart failure and ischemia in patients with heart disease and kidney disease. However, no study has shown that the other two PHD subtypes have difference in functions.
One of the important roles of HIF is to activate the expression of erythropoietin (EPO) in living organisms. As a glycoprotein hormone, EPO can stimulate red blood cell proliferation, differentiation and maturation. EPO on the one hand can stimulate bone marrow hematopoietic function, timely and effectively increase the number of red blood cells, thereby enhancing the oxygen carrying capacity of the blood. On the other hand, EPO can enhance the body's oxygen binding, transport and supply capacity, and improve hypoxia conditions. Under normal physiological conditions, EPO is mainly synthesized and secreted by the kidney, therefore, a patient with kidney failure will suffer from ischemia because EPO cannot be normally synthesized in the body. In the late 1980s, Amgen company first successfully achieved industrialization of EPO and gradually applied EPO to the patients with anemia caused by chronic kidney failure, AIDS, cancer and chemotherapy. However, with the huge development of EPO generation and application, exogenous EPO administration still faces several problems: 1, EPO is expensive, and is a great burden especially for the patients who need long-term use; 2, as a macromolecule glycoprotein, EPO also has the characteristics of low bioavailability, short half-life in the organism, easy to be hydrolyzed by the enzyme in the gastrointestinal tract, so EPO must be frequently administrated by injection, which limits the probability of patient's self-administration, and brings great inconvenience to the patients; 3, Industrially synthetic EPO still cannot avoid the immunogenicity and the product has certain medication risks.
Due to these problems in the use of exogenous macromolecule EPO, it will be very promising to replace exogenous EPO and bring the patients more choices by developing small molecule HIF prolyl hydroxylase inhibitors to inhibit the HIF-a degradation, thereby stimulating the generation of endogenous EPO in human body.
So far, two HIF prolyl hydroxylases, Akebia's AKB-6548 and Fibrogen's FG-4592, have been introduced into the clinical phase II study. (Refer to WO 2012170377A1, US2010331374A1, US2010305097A1, US2007299086A1, US2004254215A1, US2007298104A1, US2009082357A1, US2010113444A1, WO2013134660, WO2010059552A1).
